Irrigation system vs. hand watering

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By Adrian Higgins
Thursday, July 15, 2010

I'm casting my mind back to mid-March: Three feet of snow has melted at last, and though I've lost vital garden-preparation time, the gutters are hanging off the house and the trees are down, there's one thing I don't have to worry about: The soil will never dry out again.

Ha.

The heat and dryness in the Washington area have been building since May, but furtively. An inch or more of rain in the past week has brought us back from the precipice, but not far. I didn't realize how seriously dry things had become until I drove into the Virginia countryside three weeks ago to see roadside embankments straw-colored and the hayfields stunted. Gardeners in the country who rely on well water were already in a bind before the intervening weeks piled on more hot and humid conditions.

Any gardener will tell you that plants seem to thrive on rain but merely survive on tap water -- it's one of the mysteries of the enterprise -- but at least we townies have water, the recent restrictions in Maryland notwithstanding.

When the weather turns dry, readers urge me to commend arid-zone gardening, with tap-rooted succulents and wildflowers that endure drought. The problem, however, is that Washington isn't Colorado or California. We get blizzards and tropical storms and plain old spring gully washers that soak the clay soil and dictate a range of plants that grow lush but need a fair amount of soil moisture. We don't typically suffer the water deficiencies found in the Southwest, though we can in some years.

But access to water, and a valid need to water the type of plants we must grow here, doesn't mean we should squander it. Driveways and sidewalks don't need sprinkling, though this reality is clearly lost on many.

Automatic vs. hand watering

Automatic irrigation systems can work effectively, but there is something about them that I find distasteful. You wonder if they have been installed to remove the owner from actually having to fuss with the vegetation. They also work against plants, including trees that decline in constantly soggy conditions. And as a gardener friend pointed out, a sprinkler head in May might do its job. By July, a burly perennial like a big hosta may have smothered the thing, luxuriating while its neighbors are gasping.

Hand watering takes time but permits you to see what needs water the most. A wand attachment delivers a lot of water, but softly. A hose-end sprayer is a disaster. Having a riot of color in your flower beds is one thing; turning a water cannon on the poor things is quite another. The water delivers force but not volume, so the flowers are beaten up while remaining dry.

Experienced gardeners just put their thumbs over the end of an open hose to deliver water near and far, sparingly or by the gallon, but in a controlled and relatively gentle fashion.

What needs a soak?

Diligent watering is nowhere more important than in the vegetable garden. Plants grown for their fruit will be grudging and sick if drought stressed. Peppers and tomatoes develop a disease called blossom end rot if yanked by dryness. Deep, amended garden beds that are mulched need to be soaked only twice a week to support healthy plants, though seedlings and transplants will need watering more often.

Container watering is easy, but like everything else in the garden it requires forethought. The larger the container, the less watering it will need. Terra cotta pots dry out more quickly than those of plastic or glass fiber. The soil line should be at least an inch below the rim of the pot, to capture lots of water while you move to the next container, and a pot isn't watered until you see it drain.

The lawn can be fixed in September; now, young trees and shrubs particularly need your attention. In my garden, any woody plant put in since 2008 gets hand-watered with a four-gallon watering can at least once a week.

Street trees need your help, young ones critically. Older ones have compromised root systems due to their location and also benefit from a soak. As Marc Buscaino of Casey Trees points out, clay soil that has dried out actually repels water. A hose on a trickle for 20 minutes will allow water to seep into the ground and make it more receptive to future irrigation. If you can't get a hose to your curbside trees, you can drill holes in the bottom of a five-gallon bucket and haul it to the root zone (quickly; don't stop to chat with the neighbor). Casey Trees, the nonprofit booster of the city's urban forest, suggests an application of 25 gallons a week in the absence of rain.

More tips

What is vexing a lot of my fellow gardeners is that their gardens dried out with much of July and August still to go. Some rains now may help, but it's unlikely the soil will have enough moisture without some continued effort this year from us. The Maryland Home and Garden Information Center has some great online advice for coping with the weeks ahead at http://www.hgic.umd.edu/content/timelytips.cfm.

I anticipate kicking up a lot of grasshoppers -- we tend to get such plagues in dry years -- as well as spider mite damage, especially on conifers. Hose the foliage and water the roots. Lay off the fertilizers and pesticides if your plants are drought- and heat-stressed; they will do more harm than good.

On the bright side, Japanese beetles like to lay eggs in the lawn at this time of year but have a devil of a time trying to do so on rock-hard soil. They will be drawn to turf that is lush and green with fancy irrigation systems.

I plan to spend the weekend working on my thumb-over-hose technique and thinking about the next blizzard.

Follow @posthiggins on Twitter.


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